Politeness has a place, but not in high-stakes situations, according to researchers.

Whether a pilot is making an emergency flight or a doctor is trying to help a patient make a surgical decision, the sort of vague, evasive responses that help us avoid hurting someone’s feelings can have disastrous consequences, according to a team of scientists, including Jean-François Bonnefon and Wim de Neys of the National Center for Scientific Research and the University of Toulouse in France, and Aidan Feeney of Queen’s University in the United Kingdom.

The more sensitive an issue, the more polite we tend to become, according to the researchers.

But, because it can require us to become evasive and vague, politeness can have a downside: It can lead to uncertainty about what the polite person is actually saying. As a result, we have to spend more mental resources trying to parse the actual meaning, the researchers write in their review of past studies on politeness in the October issue of the journal Current Directions in Psychological Science.